The present invention relates to imaging systems and image sensors used for providing a good image captured by an on-vehicle camera or the like which requires high reliability and is often used under white light or low color rendering illumination.
For the purpose of enhancing the safety of running vehicles, many systems have been conventionally proposed in which imaging means such as a video camera or the like is provided in a vehicle to monitor images around the vehicle.
Specifically, a visual recognition support system in which an output of a camera mounted in a door mirror, a side mirror or the like is displayed in an image display device provided near a driving seat in a vehicle to help a driver check conditions for oncoming vehicles and a next traffic lane, images of vehicle's blind spots in the horizontal direction and the like, and a recognition system for performing processing of taken-in images to detect motions of surrounding vehicles and then giving a warning to a driver depending on distances from the surrounding vehicles and speeds of the vehicles, or detecting a predetermined position where a roadway region and recognizing signs.
Such an on-vehicle camera has to be unaffected by climate conditions. For example, to achieve an imaging system which is unaffected by climate conditions, Japanese Laid-Open Publication No. 5-294183 discloses a technique in which a mirror portion of a door mirror of a vehicle is formed to be a half mirror, a video lens with an optical filter mounted and CCD or like device are disposed therein, an image signal processed by a camera signal processing circuit disposed in a passenger compartment is output to an image display device.
Moreover, in Japanese Laid-Open Publication No. 5-294183, a technique is disclosed to solve the following problems with respect to camera mounting positions, i.e., 1) if a camera is disposed in a passenger compartment, appearance and interior comfort are deteriorated and driver's field of view is narrowed, 2) if a camera is disposed in an engine room, the surrounding environment is very bad and failure of a camera is caused, 3) if a camera is disposed in an outer peripheral portion of a vehicle, specifically, on a door side or on an engine room, harmful effects in terms of safety, design and performance such as aerodynamic drag are caused.